Summary of Work: The purpose of this intra-agency agreement (Y02-AG-5-0282) is to support the measurement of arterial pulse wave velocity (APWV) as a measure of arterial stiffness in the NHLBI Activity Counseling Trial (ACT). The trial is designed to test the hypothesis that increases in physical activity resulting from educational interventions will reduce arterial stiffness. The setting is appropriate for this hypothesis testing because of the prospective nature of the study and the range of interventions which will be adopted. The measurements will be taken at three points in time when other physiologic measures are taken. This will allow assessment of intra-individual variability as well as the possibility of examining change over time in these measures in relation to the level of compliance with the physical activity intervention. The study is taking place in three geographic locations to assure adequate sample size for subgroup analysis: Memphis, TN, Dallas, TX and Palo Alto, CA. Pulse wave velocity is being measured by two Doppler flow velocity probes simultaneously measuring the carotid and femoral arteries. A computer algorithm calculates average flow velocity tracings on a beat-to-beat basis. The time needed for the pressure wave to travel from the proximal to distal sampling site is calculated from the foot of the pressure wave. The baseline and 6-month examinations have now been completed, with approximately 500 APW tracings available for analysis. Quality control reports from the Coordinating Center indicate that a very high proportion of the tracings are of acceptable quality and will be useful for analysis. Personnel from the Reading Center in Baltimore have developed a protocol for decision making with regard to inclusion of multiple records from the same individual analysis. This followed an extensive evaluation of the reproducibility of repeated records from the same individual conducted by the Reading Center, with collaboration from the coordinating center and the EDB staff. Presently the clinics are in the midst of completing the 24-month follow-up APWV measurements, and the quality of the readings appears to remain at a high level. It is expected that the data collection will be completed in the spring of 1999. Plans are under way for analysis of the baseline data and preparation of manuscripts. The final baseline data set has been transmitted to the Coordinating Center from the Reading Center. Computing work required for the baseline data analysis will be completed by the Coordinating Center.